In the case of producing reduced iron by the reduction of iron oxide contained in iron ore, a process for producing reduced iron with relatively easily available coal that serves as a carbonaceous reducing agent for the reduction of iron ore have been receiving attention. In the process for producing reduced iron, agglomerates that contains an iron oxide-containing substance, a carbonaceous reducing agent, and a melting point-adjusting agent are charged into a movable hearth type heating furnace, such as a rotary hearth furnace, and heated by gas heat transfer and radiation heat with a heating burner in the furnace to reduce iron oxide, thereby producing agglomerate reduced iron. The process for producing reduced iron has the following advantages: in addition to the coal basis, powdery iron ore can be directly used; iron oxide in iron ore can be rapidly reduced during reduction because iron ore and the reducing agent are juxtaposed to each other; a large-scale facility, such as a blast furnace, is not required; and coke is not required.
As the foregoing process for producing reduced iron, the applicants propose a technique described in PTL 1. The technique is one in which a raw material that contains a metal oxide-containing substance and a carbonaceous reducing agent is heated to reduce the metal oxide in the raw material and in which the resulting metal is further heated so as to be melted while allowing the metal to separate from a by-product slag component and allowing the by-product slag to coalesce, in which a coalescence-promoting agent for the by-product slag is mixed with the raw material. The mixing of the coalescence-promoting agent for the by-product slag promotes the separation of the resulting molten metal from the by-product slag, thereby producing a high-purity granular metal having a relatively large size, and a uniform particle diameter with high productivity in satisfactory yield. It is disclosed that calcium fluoride (CaF2) serving as the coalescence-promoting agent for the by-product slag is mixed.